Electric furnace



Aug. 7, 1934. v. H. SANDERS ELECTRIC FURNACE 2 Sheets-Sheet 1 Filed Feb.23, 1933 INVENTOR Wrnon H. Sanders mm m,

ATTORNEYS 1934. v. H. SANDERS 1,969,478

ELECTRIC FURNACE 2 Sheets-Sheet 2 Filed Feb. 25, 1933 I IIIIIIIII' 4'IIIIIIIIII INVENTOR Viv-non II. Sanders ATTORNEYS Patented Aug. 7, 1934UNITED STATES PATENT OFFICE ELECTRIC FURNACE Application February 23,1933, Serial No. 657,976 In Canada November 9, 1932 Claims.

This invention relates to electric furnaces designed for heatingarticles as they are fed through a tubular passageway, the tube being aresistance element composed mainly of a material such as carbon whichhas a relatively high electrical resistance and which is intenselyheated by the passage of a current of high amperage therethrough.

An object of the present invention is to provide 10 a construction inwhich the heating tube is effectually insulated to retain the heatgenerated therein and effectually protected from contact with air toprevent deterioration of highly heated portions of the tube byoxidation.

A further object of the invention is to provide a furnace of thecharacter described in which the heat losses are small and in whichthere is an efiective interchange of heat between incoming and outgoingmaterial passing through the tube.

A further object is to provide a furnace structure in which the outercasing is formed of metal and is substantially air-tight and in whichmeans is provided for conducting current through a portion of the carbontube with a minimum loss. A further object is to provide electrodes inthe form of suspension members which serve" to support the heated tubeintermediate its ends.

A further object is to provide means permitting escape of gases from theinterior of the tube,'to-

. gether with means for controlling the discharge of gases.

With the above and other objects in view, the

invention may be said to comprise the furnace as Figure 1 is a top planiview of a furnace.em-

4 bodying the invention;

central longitudinal section;

' at 4 -4"in 'Fig'; 2'; A

through one end of "the carbon tube and the 'cas ing forming anextension of the tube;

, Fig. 2 is,,aside elevation of the'furnace with:

a portion thereof"bmken"a'way.and ls'hownim the top of the'furnace. Thevertical end'porl Fig-l4 isa section taken 'onthe line' indica'ted" Fig.6 is a section taken on the line indicated at 6-6 in Fig. 5.

Referring to the accompanying drawings, the outer shell of the furnaceis in the form of a box-like metal casing constructed of sheet metalplates and having riveted or welded joints. This casing has a bottom 1,side walls 2, and end walls 3. Extending longitudinally through thecasing centrally thereof there is a tube 4 formed-of high resistancematerial such as carbon which has a central longitudinally extendingpartition 5 which divides the interior of the tube into two passages 6and '7. The tube 4 is preferably rectangular in cross section and thepartition 5 extends upwardly from the bottom of the tube centrallythereof.

Articles to be heated indicated at 8 in Fig. 6 are fed through thepassages 6 and '7, the articles on one side of the partition 5 beingadvanced in one direction and the articles on the opposite 5 side of thepartition being advanced in the opposite direction.

The opposite ends of the carbon tube 4 are disposed in openings 10 inthe end walls 3 and are seated in collars 11 secured to the outer sidesof so the walls at the margins of the openings 10. At each end thereofthe casing has tubular extensions in the form of castings 12 which aresecured to the collars 11 and form continuations of the carbon tube 4.The extensions 12 serve to lengthen the passages for the material sothat a more complete interchange of heat between the previously heatedarticles and the cold articles is effected. Each of. the tubularextensions 12 is closed at its outer end by a door '13 which is carriedby a hinged bar 14 which swings about a pivot 15 and which is providedwith a latch 16 near its free end which engages with a suitable keeperon the casting.

Each door 13 has a loose connection with its supporting bar 14 and isadapted to be pressed tightly against the end of the extension 12 tosealthe end thereof by means of a screw 17 which is threaded in the bar andengages; the door 13.

.Intermediate the ends, of the furnace two cross bars lfl which are bentto U-shape extend across Fig- 3 is a section taken on the line indicateda t1ons of these cross ba ale secured at their lower endsftolongitudinal bars 19 attachedto the upper edges rifthefs'ide walls 2 ofthe casing. The cross baifslS are 'spac'edfap'artlongitudinally of the 3s f furnace. each) cross bar serving as a support for an Fig. v5 is: axfragmentary lOngitudinal QsectiOn" electrode connected to thecarb'ontube 4 so that of the electrodes is suspended from central por tions ofa cross bar 18 by means of suspension rods 20 which are attached towater cooling heads 21, each of which is clamped to a pair of electrodebars 22, which may be composed of carbon, by means of a cross bolt 23.The electrode bars 22 which are composed of electrically conductivematerial are spaced apart a distance correspond ing to the width of thecarbon tube 5 and engage with opposite side walls of the tube. Theelectrode bars 22 extend below the carbon tube 4 and between their endsthere is secured a spacer block 24.

Above each of the spacer blocks 24 there is an insert 25 of electricallyconductive material which engages the bottom wall of the tube andbetween each pair of electrode bars above the tube there is an insert 26of electrically conductive material which engages the top wall of thetube.

Seated at its ends on the spacer blocks 24 there is a longitudinal beam27 upon which the tube 4 rests from one electrodeto the other. The upperends of the electrodes are preferably cooled by water supplied to theheads 21 through pipes 28. Suitable electrical connections are providedat the upper end of each electrode for supplying current thereto.

Midway between the two electrodes a pair of arched cross bars 29 extendsacross the top of the casing and directly over the tube 5 the cross bars29 support a water cooling head 30 through which extends a stack 31which communicates at its lower end with the interior of the carbon tube4 and provides a passage for the escape of gases from the interior ofthe tube. Suspension rods 32 extend downwardly from the head 30 andbeneath the beam 2'7 to provide an additional support for the tubeintermediate the electrodes.

At its upper end the stack 31 is provided with a hinged closure member33' which is adapted to be opened or closed by actuation of a connectingrod 34 which is attached at its lower end to the hinged closure member33 and its upper end to a. crank 35 which is positioned midway betweenthe ends of a shaft 36 which is journaled in studs 37 extending upwardlyfrom opposite ends of the casing. At each end the shaft 36 is providedwith a hand crank 38 so that an operator standing at either end of thefurnace can actuate the closure member 33 to open or close the stack 31.It is desirable to close the stack to prevent an inrush of air when thedoor at either end of the furnace is opened to remove articles whichhave passed through the furnace and to insert articles which are to bepassed through the furnace. The central portion of the heating tube israised to a very high temperature and opening of the end of the tubewould cause an inrush ofair through the stack and a blast of heatedgases through the open end of the tube 4 if the stack 31 were leftopened. After the carbon tube has been assembled in the casing with theelectrodes and central stack, the entire box-like casing is filled witha suitable insulating material such as lamp black, and the top of thecasing is closed by means of a sheet metal roof 40 composed of archedplates and the Joints sealed with high temperature cement. Openings 41are preferably provided immediately adjacent the electrodes so thatadditional lamp block can be delivered into the interior of the casingto replace any lamp black which may be consumed during operation of thefurnace.

Since an alternating current of very high amperage is passed through theelectrodes, it is denimble that there be no magnetic material in thecasing structure surrounding the electrodes. For this reason the crossbars 18 are made of U- shape with their vertical end portions adjacentthe side walls and with the central portions from which the electrodesare separated spaced above the tops of the electrodes. The sheet metalof the roof is preferably composed of a. non-magnetio metal, such ascopper or brass.

In the operation of the furnace the articles to be heated are insertedone after another into one end of one of the longitudinal passagewaysthrough the tube 4, and into the opposite end of the other longitudinalpassageway, so that as the operation progresses the articles will travelin one direction through one of the passageways and in the oppositedirection in the adJoining passageway.

As before explained, the electric current passing through the centralportion of the carbon tube 4 generates a very intense heat which istransmitted to the articles in the passageways as the articles passthrough this central heating zone. In the outer end portions of the tube4 the articles in one passageway which have been intensely heated duringtheir passage through the heating zone transfer a considerable portionof their heat to articles in the adjoining passageway which are beingmoved toward the heating zone.

In order to avoid the necessity of opening the ends of the carbon tube 4each time an article is introduced into or taken out of the tube, pushrods 42 may be provided in the doors 13. These rods are slidably mountedin the doors extending through packed openings in the doors, the rod inone door being centrally disposed with respect to the passage 6 and therod in the other door being centrally disposed with respect to thepassage 7, so that articles in the two passages may be advanced bypushing the rods through the doors, therebymaking it possible to removeseveral of the articles which have been heated and insert severalarticles to be heated each time the doors 13 are opened.

The location of the hand cranks 38 convenient to an operator standing ateither end of the furnace enables the operator to quickly close thestack as either door 13 is being opened so as to avoid an outrush ofheated gases.

Since the central portion of the carbon tube is heated to a very hightemperature it is essential that the tube be effectually. insulated andthat air be excluded from this portion of the tube. This is accomplishedby providing. an outer casing which is substantially air-tight and aninsulating filling closely packed within the casing. It is also highlyimportant that the carbon tube be so supported in the furnace that verylittle of the heat will be conducted to the walls of the casing, andthat the supporting members be ccpable of withstanding the heat withoutserious distortion. The supporting of the tube by means of suspensionmembers which also serve as electrodes provides a support for the .tubewhich does not supply a path for the passage of heat to the Furthermore,the construction is relatively 1w 7 time.

Aside from the specific embodiments of the invention herein shown anddescribed, it will be understood that numerous details of constructionmay be altered and omitted without departing from the spirit and scopeof this invention, and it is. not intended to limit the invention to theexact construction set'forth, as it is desired to claim the inventionbroadly as well as specifically, as indicated in the appended claims.

What I claim is:

1. An electric furnace comprising an outer sheet metal casing, a heatingelement in the form of a tube of a size suitable for passage of materialtherethrough extending centrally through the casing from end to end andcomposed of an electrically conductive material of high resistance,insulating material filling the casing exteriorly of the tube, and meansfor supporting the central portion of the tube from the top of thefurnace including spaced suspension members engaging the tube inwardlyof the ends of the casing, said members being in the form of electrodesfor connecting the heating tube to a source of current.

2. An electric furnace comprising an outer air excluding casing, acentrally disposed heating element in the form of a carbon tube of asize suitable for the passage of material therethrough and extendingcentrally through the casing, insulating material filling the casingexteriorly of the tube, supporting members extending across the top ofthe casing, and means for suspending said tube from said cross'membersand for passing a current of electricity through a portion of said tube.

3. An electric furnace comprising an outer air excluding casing,acentrally disposed heating element in the form of a carbon tube of asize suitable for the passage of material therethrough and extendingcentrally through the casing, insu-' lating material filling the casingexteriorly of the tube, supporting members extending across the top ofthe casing, means for suspending said tube from said cross members andfor passing a current of electricity through a portion of said tube,means for opening and closing the ends of said tube, and a stackcommunicating with the portion of the tube through which current ispassed.

4. An electric furnace comprising an outer air excluding casing, acentrally disposed heating element in the form of a carbon tube of asize suitable for the passage of material therethrough and extendingcentrally through the casing, insulating material filling the casingexteriorly of the tube, supporting members extending across .the top ofthe casing, means for suspending said tube from said cross members andfor passing a current of electricity through a portion of said tube,means for opening and closing the ends of said tube, a stackcommunicating with the portion of the tube through which current ispassed, and means for opening and closing said stack.

5. An electric furnace comprising an outer air excluding casing, acentrally disposed heating element in the form of a carbon tube of asize suitable for the passage of material therethrough and extendingcentrally through the casing, insulating material filling the casingexteriorly of the tube, supporting members extending across the top ofthe casing, means for suspending said tube from said cross members andfor passing a current of electricity through a portion of said tube,said means comprising electrodes connected adjacent their upper ends tosaid supporting members and adjacent their lower ends to said tube tosupport the same.

6. Anelectric furnace comprising a metal casing having centrallydisposed openings in its opposite end walls, a carbon tube through whichmaterial may be passed extending longitudinally through the casing andhaving its ends seated in said openings, tubular members secured to theexterior of said end walls and forming'continuations of the carbon tube,doors for closing the outer ends of said extensions, insulating materialfilling the casing exteriorly of said carbon tube, spaced electrodesconnected to said tube intermediate its ends, and a stack communicatingwith the interior of said carbon tube intermediate said electrodes andextending through the top of the casing to permit escape of gases.

'1. An electric furnace comprising an outer casing having a top wallcomposed of non-magnetic metal, a carbon tube forming a passage formaterial through the casing from end to end centrally thereof,insulating material filling the easing exteriorly of the tube, andelectrodes extending through the top wall and connected to the carbontube at spaced points.

8. An electric furnace comprising a box-like casing, a carbon tubeforming a passage for material extending centrally through the casingfrom end to end, insulating material filling the casing exteriorly ofthe tube, spaced supporting members extending across the top of thecasing transversely of the tube, and electrodes supported by said crossmembers and supporting the tube at spaced points.

9. An electric furnace comprising a box-like casing, a carbon tubeforming a passage for material extending centrally through the casingfrom end to end, insulating material filling the casing exteriorly ofthe tube, spaced supporting members extending across the top of thecasing transversely of the tube, electrodes supported by said crossmembers and supporting the tube at spaced points, and a stackcommunicating with the tube intermediate the electrodes.

10. An electric furnace comprising a box-like casing, a carbon tubeextending across the casing centrally thereof, insulating materialfilling the casing exteriorly of the tube, electrodes connected to thetube at spaced points, a stack communicating with the interior of thetube, means for opening and closing the ends of the tube, a movableclosure member for opening and closing the stack, and means accessibleto an operator adjacent either end of the tube for actuating saidclosure member.

VERNON H. SANDERS.

